📐 Perimeter Calculator
Calculate perimeter of shapes
How to Use This Calculator
Select Shape
Choose the shape type: Rectangle, Square, or Circle (Circumference).
Enter Dimensions
Input the required dimensions for your selected shape (length and width for rectangle, side length for square, or radius for circle).
Click Calculate
Press the "Calculate Perimeter" button to get the perimeter (or circumference for circles).
Formulas
Rectangle
Perimeter = 2 × (Length + Width)
P = 2(l + w)
Square
Perimeter = 4 × Side
P = 4s
Circle (Circumference)
Circumference = 2 × π × Radius
C = 2πr (where π ≈ 3.14159)
Example 1 (Rectangle): Find perimeter of rectangle with length = 10, width = 5
Perimeter = 2 × (10 + 5) = 2 × 15 = 30 units
Example 2 (Square): Find perimeter of square with side = 8
Perimeter = 4 × 8 = 32 units
Example 3 (Circle): Find circumference of circle with radius = 5
Circumference = 2 × π × 5 = 10π ≈ 31.42 units
About Perimeter Calculator
The Perimeter Calculator helps you find the perimeter (or circumference for circles) of common geometric shapes. Perimeter is the total distance around the outside of a shape, measured in linear units.
When to Use This Calculator
- Construction: Calculate fencing needed around a yard, garden, or property
- Landscaping: Determine edging or border material requirements
- Architecture: Calculate perimeter for building foundations or structures
- Education: Learn and practice perimeter calculations
- Design: Calculate frame dimensions for artwork or designs
- Real Estate: Estimate property boundaries and fencing costs
Why Use Our Calculator?
- ✅ Multiple Shapes: Supports rectangles, squares, and circles
- ✅ Instant Results: Get perimeter immediately
- ✅ Step-by-Step Display: See calculation formulas with your values
- ✅ Works with Any Units: Meters, feet, inches, or any unit of measurement
- ✅ 100% Accurate: Precise mathematical calculations
- ✅ Completely Free: No registration required
Understanding Perimeter
Perimeter is the total distance around a two-dimensional shape. Key concepts:
- Linear Measurement: Perimeter is measured in linear units (meters, feet, inches, etc.)
- Sum of Sides: For polygons, perimeter = sum of all side lengths
- Circle Special Case: For circles, perimeter is called "circumference" and uses π
- Different from Area: Perimeter is a length (1D), while area is space (2D)
- Real-World Use: Used to measure boundaries, fencing, frames, and edges
Real-World Applications
Fencing: To fence a rectangular yard that is 20 meters long and 15 meters wide, you need a perimeter of 2 × (20 + 15) = 70 meters of fencing material.
Circular Path: For a circular walking path with radius 10 meters, the path length (circumference) is 2 × π × 10 ≈ 62.83 meters.
Picture Frame: To frame a square photo with 8-inch sides, you need 4 × 8 = 32 inches of frame material.
Frequently Asked Questions
What is perimeter?
Perimeter is the total distance around the outside of a two-dimensional shape. It's measured in linear units (meters, feet, inches, etc.) and represents the boundary length.
What's the difference between perimeter and area?
Perimeter is the distance around a shape (1D - length), measured in linear units. Area is the space inside a shape (2D - surface), measured in square units. For example, a 10×10 square has perimeter = 40 units but area = 100 square units.
How do you calculate perimeter of a rectangle?
Rectangle perimeter = 2 × (length + width). This formula adds all four sides: length + width + length + width = 2(length + width).
What is circumference?
Circumference is the special name for the perimeter of a circle. It's calculated as C = 2πr, where r is the radius, or C = πd, where d is the diameter.
Can I use different units for length and width?
No, both dimensions must use the same units for accurate perimeter calculation. If length is in meters, width should also be in meters. The perimeter will be in meters.
How do I find perimeter if I only know the area?
For some shapes, you need additional information. For example, a rectangle with area 100 could be 10×10 (perimeter 40) or 20×5 (perimeter 50). You need at least one dimension to find perimeter from area.
Why is π used in circle circumference?
The circumference of a circle is always π times the diameter (or 2π times the radius). This is a fundamental geometric relationship discovered in ancient times. π ≈ 3.14159 is the ratio of any circle's circumference to its diameter.